Low pressure mercury vapor discharge lamp radiating germicidal and erythemal rays in ratio of less than 1.5

ABSTRACT

A low pressure mercury vapor discharge lamp emitting erythemal rays and germicidal rays includes an envelope on the inner surface of which there is coated with an erythemal ray emitting film for transmitting to the outside of said envelope visible straight light beams within the range of 45 to 75 percent.

United States Patent 1 Someya et a1.

[ Feb. 6, 1973 [54] LOW PRESSURE MERCURY VAPOR DISCHARGE LAMP RADIATING GERMICIDAL AND ERYTH EMAL RAYS IN RATIO OF LESS THAN 1.5

Q [75] Inventors: Akira Someya; Kohtaro Kohmoto,

both of Yokohama, Japan [73] Assignee: Tokyo Shibaura Electric Co., Ltd., Kawasaki-shi, Japan I 22 Filed: ,Iune3, 1971 21 Appl.No.: 149,437

Related US. Application Data [63] Continuation-impart of Ser. No. 812,264, April 1,

.1969, abandoned.

[521 [1.8. CI. ..3l3/l09, 313/112, 313/221 [51] Int. ..H0lj 61/30, 1101 61/44 [58] Field otSea'rch ..313/109,221,112'

[56] References Cited UNITED STATES PATENTS 2,445,692 7/1943 Porteretal ..313/109 2,362,384 11/1944 Libby ..313/221 X 2,362,385 11/1944 Libby .313/221 X 3,150,281 9/1964 Bishay .3..3l3/221 2,447,210 8/1948 Roberts..... ....313/109 2,424,454 7/1947 Gordon ....313/109 2,355,258 8/1944 Biggs et al. ..3l3/109 OTHER PUBLICATIONS Fluorescent Lamps and Lighting, by Elenbaas et -al.,

Chapter II, 1962, pp. 22-23, Sec. 2.3 R, other-phosphers.

Primary ExaminerPalmer C. Demeo Attorney-Flynn & Frishauf [57] ABSTRACT A low pressure mercury vapor discharge lamp emitting erythemal rays and germicidal rays includes an envelope on the inner surface of which there is coated with an erythemal ray emitting film for transmitting to the outside of said envelope visible straight light beams within the range of 45 to 75 percent.

2 Claims, S 'DraWing Figures PATENTEDFEB 6 ma SHEET 10F 2 FIG.1

FIG.2

WAVELENGTH FIG.3

H II I LOW PRESSURE MERCURY VAPOR DISCHARGE LAMP RADIATING GERMICIDAL AND ERYTHEM AL RAYS IN RATIO OF LESS THAN 1.5

CROSS-REFERENCE TO RELATED APPLICATION This is Continuation-in-part of the U.S. Pat. application Ser. No. 812,264, filed on Apr. 1, 1969, now abandoned.

BACKGROUND OF THE INVENTION v originally designed for simultaneous realization of the effect of both rays, such prior art lamp had a low luminescence efficiency'and a relatively short life, and

was not adapted particularly for livestock breeding for t which both rays should be generated in a prescribed ratio.

SUMMARY OF THE INVENTION It is accordingly the primary object of this invention to provide a low pressure mercury discharge lamp capable of efficiently generating germicidal and erythemal rays at the same time and having its life prominently extended.

Another object on the invention is to provide a low pressure mercury discharge lamp adapted to' breed livestock, particularly chickens and pigs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation, with part broken away, of a low pressure mercury vapor discharge lamp according to an embodiment of the present invention;

FIG. 2 is a diagram of the spectro-transmission curve DESCRIPTION OF THE PREFERRED EMBODIMENTS Irradiation of ultraviolet rays (253.7 nm) to livestock, for example, pigs or chickens has generally been supposed to have a harmful effect, because such rays are likely to injure the cellular tissues of these creatures. However, the inventors study and experiments of long years show that the aforesaid view is wrong, namely, that application of ultraviolet rays (253.7 nm) together with erythemal rays (280.0 to 340.0 nm) in the suitable ratio to livestock, particularly to chickens at the rate of several hours per day produced the undermentioned effect.

The parts of the chicken body or surroundings exposed to a combination of germicidal and erythemal rays were directly sterilized. Since the air in the chicken house was disinfected every day, disease germs were exterminated, though they might temporarily intrude therein. The occurrence of diseases, for example, the Newcastle disease, was reduced, proving the preventative effect of said rays. Various germs prevailing in the chicken house were substantially stamped out, so that the bad smell peculiar to the chicken house was appreciably eliminated, contributing to the prevention of a public nuisance.

Application of combined sterilizing and erythemal rays had a further advantageous effect of promoting the health of chickens, elevating the rate of laying eggs, reducing their death rate, minimizing the possibility of soft or broken eggs being laid and accelerating the growth of chickens. Furthermore, there was observed no harmful effect of, for example, destroying the cellular tissues of chickens which application of said rays was expected to give. Based on the aforementioned ex-.

' fluorescent materials such as calcium zinc phosphate associated with an envelope used in said mercury vapor and/or lead activated calcium silicate and is so designed as to cause 45 to 75 percent of visible straight light beams to be transmittedvto the outside of an envelope, so that the germicidal and erythemal rays may be radiated in the ratio less than 1.5. Where applied to livestock breeding, the discharge lamp of this invention displays the aforementioned effect. For example,

time will not have a harmful effect on chickens. In con- I trast, the discharge lamp set forth in the aforesaid U.S. Pat. No. 2,445,692 projects ultraviolet and erythemal rays in the ratio of 1.5 to 9, that is, the ultraviolet rays accounting for considerable percentage. Therefore, where erythemal rays are emitted at the above-mentioned rate of 0.2 to 1.0 E-viton hr/cm per day, the amounts of ultraviolet rays radiated at the same time prominently exceeds the allowable limit, causing cocks to present parched crest and hens to lay a decreased number of eggs, that is, fowls as a whole to be undergrown.

There will now be described by reference to FIG. 1 a low pressure mercury vapor discharge lamp according to an embodiment of the present invention. An envelope or bulb l0 assumes a narrow cylindrical form and has a pair of electrodes 11 and corresponding bases 12 sealed tob'oth ends. The envelope 10 is formed of ordinary ultraviolet-ray transmissible glass or germicidal glass which allows more than per cent of ultraviolet rays (253.7 nm) and less than about 20 per cent of mercury resonant lines (185.0 nm) generating health-injuring ozone to be transmitted. The inner surface of the envelope 10 is coated with a health-promoting fluorescent layer 13 consisting of calcium zinc phosphate in a suitable thickness (for example, 0.003 gr/cm") or preferably to such extent that the transmission 1 of visible straight light beams attains 45 to per cent. The term transmission of visible straight light The fluorescent layer is not limited to the aforemen- I tioned material, but may be formed of any material, for example, lead activated calcium silicate which can mainly give forth erythemal rays (280.0 to 340.0 nm).

, There will now be given the reason why the thickness of the fluorescent layer is limited preferably to the range of 1' 45 to 75 per cent. As apparent from FIG. 2, the germicidal glass or boron silicate glass used in the aforementioned embodimenthas the transmissionwaveleng'th characteristics of allowing approximately 80 per cent of ultra-violet rays (253.7 nm) to be transmitted to the outside of a lamp. Referring to FIG. 2 the ordinate represents transmission (percent) and the abscissa wavelength (nm), transmission at the respective wavelengths being denoted by curve A.

A lamp using an envelope prepared from boron silicate glass presents'such a distribution of spectro-energies as shown in FIG. 3. In FIG. 3, the ordinate represents relative energies, the abscissa wavelengths (nm), the radiated energy of ultraviolet rays (253.7 nm) and Q, the energy of erythemal rays (peak value: 310.0 nm) radiated from a fluorescent layer 13. As seen fromv FIG. 3, substantially 100 per cent of the erythemal rays emitted from the fluorescent layer 13 are allowed to pass to the outside of the envelope.

FIG. 4 presents the values measured, when the thickness of the fluorescent layer is varied, of the per cent energy 0, of germicidal rays radiated to the outside of the lamp, the per cent energy Q of erythemal rays similarly radiated to the outside, the total per cent energy Q of both rays thusradiated and ratio of Q, to Q In FIG. the left ordinate designates the amount of energy released to the outside of the lamp, the right ordinate the ratio of Q, to Q and the abscissa the transmission of visible straight light beams. Since the transmission of visible 7 straight light beams through the fluorescent layer is in inverse proportions to the thickness of the layer, said thickness is expressed by the transmission of visible straight light beams. In this case, the kind, particle size and distribution of the comminuted material forming the fluorescent layer may be deemed constant. The results of measurement show that the total amount of radiated energy attains a maximum when the transmission 1' of visible straight light beams account for 55 to 65 per cent, namely, that if the transmission 1 of visible straight light beams is so regulated as to fall within the range of 45 to 80 per cent then the amount'of energy actually radiated outside of the envelope can be elevated to more than 90 per cent of the maximum radiation of energy. FIGS. 4 and illustrate that a range of substantially half way between the optimum values of the relative energy and maintenance factor is 60 to 65 percent. The maintenance factor is discussed below. 4

However, the inventors experiments disclose that the larger the transmission 1' of visiblestraight light beams,'i-the more reduced the output maintenance factor of rays released to the outside of the envelope. The results'of measurement associated with this fact are presented in FIG. 5. In this figure, the ordinate represents the output maintenance (percent) and the abscissathe duration of lighting the lamp (hr). The experiments also indicate that there is obtained a preferable maintenance factor when 1' "stands at below 75 per cent.- Preparation of a fluorescent layer whose thickness is sufficiently thin to allow 1' to rise above 75 per cent is 'apprecially difficult from the practical standpoint. Moreover, where the thickness of the fluorescent layer is so reduced as to cause 'r to rise higher than 75 per cent, there will be the disadvantage that the energy of erythemal rays is released outside of the envelope in smaller proportions than that of sterilizing rays. On the other hand, ifr' falls below 45 per cent, the proportions of energy of sterilizing rays emitted outside. of the lamp will, of course, be far more reduced than those of erythemal rays. Accordingly, if the thickness of the fluorescent layer is so regulated as to cause 1' to fall the range of 45 to 75 per cent, it will be possible effectively to radiate the respective sterilizing and erythemal rays without decreasing the total amount of released energy. 7

A low pressure mercury vapor discharge lamp according to the present invention of 15 W rated capacity formed of an envelope about 25 mm in outer diameter and about 436 mm long, the innersurface of which was coated with a fluorescent layer having such thickness as allowing the transmission of visible straight light beams to stand at 60 per cent, radiated sterilizing rays (257.3 nm) at the ratev equal to about 60 per cent of that obtained by the 15 W sterilizing ray lamp and'erythemal rays (280.0 to 340.0.nm) at the rate corresponding to about per cent of that realized with the conventional 20 W fluorecent sun ray lamp. The mercury vapor discharge lamp of the invention indicated about 2 ,to 2.5;rW/cmintensity of sterilizing rays and about 0. 1 E viton/cm intensity of erythemal rays at a point 2.5 meters distant. I

The aforementioned mercury vapor discharge lamp of the invention was switched on three times per day (morning, noon, and evening), each time 1 to 1.5 hours totalling 3 to 4.5 hours. The sterilizing and erythemal rays projected from the lamp were applied to grow chickens and the chicken house. As a result it was confirmed that the lamp effectively disinfected the air in the chicken house, substantially removed the objectionable odor characteristic of said house, prevented chickens from suflering infections diseases and moreover promoted their physical strength. Needless to say, the rate of laying eggs byv hens was noticeably improved.

For reference, there will now be described the experimental method used.

EXPERIMENTAL METHOD Lamp used and their arrangement (Three-tiered chicken house) Six lamps were employed at a height of 2.5 meters above the floor, the shortest distance from the chicken head being about 1 meter. Time of irradiation 5 6 number of soft or broken e s is deemed due to the 8 Morning and evening Eachtime l.5 hours, powerful effect exerted by the description and 3 hours Per precipitation of calcium in the chicken body which was promoted by mineral metabolizn.

D ofFested 3 The foregoing description relates to a low pressure Irradiated p Not irradiated mercury vapor discharge lamp of the present invention ltem H ca able of ivin forth both sterilizin and er themal T t l b ref 93752 96457 p g g y f g' e p rays at the same time. Floor space 85.8 m 85.8 m I What we claim is:

imsy lamps l0 1. A low pressure mercury vapor discharge lamp radiating germicidal and e'rythemal rays in the ratio of Results less than 1.5, comprising: em an envelo e made of ermicidal ra transmissible P g y s Deah Number Numberof glass, said envelope having a transmissivity to ulegg weight rate elected soft or month per hen out broken eggs l5 traviolet rays of more than about 70 percent and to group (gr) mercury resonant lines generating health injuring gig 1967 33': l 2? i? ozone of less than about percent; lr ra- Nov. 4014 '0 57 mercury and rare gas filled in said envelope; 25 33- g g} a pair of electrodes sealed to both ends thereof; and

2 H 20 a fluorescent la er formed of at least one material Feb 0 3 y p 1967 391) 4 48 1 selected from the group consisting of calcium zinc Not Oct. 41.1 4 4s 78 m No 3&2 0 69 76 phosphate and lead activated calcium silicate, diated Dec. 38.3 1 51 37 deposited on the inner surfaceof said envelope,

#3 1968 g said envelope and deposited fluorescent layer hav- 25 ing a transmissivity of to 75 percent of visible straight light beams. 1

As seen from above table, increase in the weight of 2. A low pressure mercury vapor discharge lamp aclaid eggs per month averaged 38 grper hen, and atmined 60 gr (even equal to tha vWeight of aboutone cording to claim 1 wheremsard envelope and deposited egg) three months after the initial irradiation. fluorescnt layer ha transmlssivity of 55 to 65 per Though it ran high in September, the death rate sharply decreased later; Particularly, reduction in the 

1. A low pressure mercury vapor discharge lamp radiating germicidal and erythemal rays in the ratio of less than 1.5, comprising: an envelope made of germicidal ray transmissible glass, said envelope having a transmissivity to ultraviolet rays of more than about 70 percent and to mercury resonant lines generating health injuring ozone of less than about 20 percent; mercury and rare gas filled in said envelope; a pair of electrodes sealed to both ends thereof; and a fluorescent layer formed of at least one material selected from the group consisting of calcium zinc phosphate and lead activated calcium silicate, deposited on the inner surface of said envelope, said envelope and deposited fluorescent layer having a transmissivity of 45 to 75 percent of visible straight light beams. 